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United States Patent |
5,699,046
|
Accolla
,   et al.
|
December 16, 1997
|
EAS system employing central and local stations with shared functions
Abstract
An EAS system employing a central station having a central processing unit
and a local station having a microcontroller and in which the functions
necessary for detecting EAS tag signals and generating alarms are shared
by the central station and the local station. A switch is further provided
at the local station for automatically reconfiguring the receiver antennas
based on antenna configuration instructions generated at the central
station responsive to certain conditions at the location being monitored.
Inventors:
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Accolla; William R. (Loxahatchee, FL);
Zampini; Michael A. (Boca Raton, FL)
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Assignee:
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Sensormatic Electronics Corporation (Boca Raton, FL)
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Appl. No.:
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551958 |
Filed:
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November 2, 1995 |
Current U.S. Class: |
340/572.4; 340/10.5 |
Intern'l Class: |
G08B 013/14 |
Field of Search: |
340/572,825.54
|
References Cited
U.S. Patent Documents
4859991 | Aug., 1989 | Watkins et al. | 340/572.
|
5214409 | May., 1993 | Beigel | 340/572.
|
5235326 | Aug., 1993 | Beigel et al. | 340/825.
|
5257011 | Oct., 1993 | Beigel | 340/572.
|
5495229 | Feb., 1996 | Balch et al. | 340/572.
|
5499017 | Mar., 1996 | Beigel | 340/572.
|
Other References
U.S. Patent Application Serial No. 08/313848, filed Sep. 28, 1994, titled
Electronic Article Surveillance Input Configuration Control System
Employing Expert System Techniques For Dynamic Optimization.
|
Primary Examiner: Mullen; Thomas
Attorney, Agent or Firm: Robin, Blecker, Daley and Driscoll
Claims
What is claimed is:
1. An electronic article surveillance ("EAS") system for detecting EAS tags
in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller and performing a function of causing
interrogation signals to be transmitted into the interrogation zone and a
function of causing signals to be received from the interrogation zone;
a central means communicating with said local means, said central means
including a central processing unit; and
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated, the plurality of functions
whose performance is shared by said central means and said local means
including signal processing functions by which the signals received by
said local means are processed.
2. An EAS system is accordance with claim 1 wherein:
said local means performs one or more of the following signal processing
functions on the signals received by said local means: variable signal
amplification, signal selection, signal combining, signal subtracting,
signal conditioning, signal enhancement and/or signal decisions; and
said central means performs at least the following signal processing
function on the signals received by said local means and transmitted by
said local means to said central means: processing to determine whether
the received signals contain EAS tag signals.
3. An EAS system in accordance with claim 2 wherein:
said local means includes: at least one variable gain amplifier for
amplifying a received signal;
and said microcontroller provides signals to said variable gain amplifier
for setting the gain of said variable gain amplifier.
4. An EAS system in accordance with claim 2 wherein:
said local means includes: a multiplexer for receiving a plurality of
received signals and selectively outputting a particular one of said
received signals for transmission to said central means;
and said microcontroller provides signals to said multiplexer for
instructing said multiplexer as to which one of said plurality of received
signals should be output by said multiplexer.
5. An EAS system in accordance with claim 2 wherein:
said central means performs the further function of reporting to said local
means when said central means determines that EAS tag signals are
contained in the signals received by said local means and transmitted by
said local means to said central means; and
said local means in response to receiving a report that the signals
received by said local means contain EAS tag signals performs the function
of generating an alarm signal.
6. An EAS system in accordance with claim 5 wherein:
the alarm signal generated at said local means results in one or more of an
audible alarm and a visual alarm.
7. An EAS system in accordance with claim 5 wherein:
said local means includes an alarm assembly;
and said microcontroller generates said alarm signal for feeding to said
alarm assembly.
8. An EAS system in accordance with claim 1 wherein:
said local means performs the function of generating an alarm signal when a
determination is made that an EAS tag is in said interrogation zone.
9. An EAS system in accordance with claim 8 wherein:
the alarm signal generated at said local means causes one or more of an
audible alarm and a visual alarm.
10. An EAS system in accordance with claim 8 wherein:
said local means includes an alarm assembly;
and said microcontroller generates said alarm signal for feeding to said
alarm assembly.
11. An EAS system in accordance with claim 1 further comprising:
a bi-directional communications path connecting the central processing unit
to said microcontroller.
12. An EAS system in accordance with claim 11 in which:
said bi-directional communications path is one of a serial and parallel
bi-directional communications path.
13. An electronic article surveillance ("EAS") system for detecting EAS
tags in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller and performing a function of causing
interrogation signals to be transmitted into the interrogation zone and a
function of causing signals to be received from the interrogation zone;
a central means communicating with said local means, said central means
including a central processing unit;
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated;
said central means performing the function of reporting to said local means
when said central means determines that EAS tag signals are contained in
the signals received by said local means and transmitted by said local
means to said central means; and
said local means in response to receiving a report that the signals
received by said local means contain EAS tag signals performs the function
of generating an alarm signal.
14. An EAS system in accordance with claim 13 wherein:
the alarm signal generated at said local means results in one or more of an
audible alarm and a visual alarm.
15. An EAS system in accordance with claim 13 wherein:
said local means includes an alarm assembly;
and said microcontroller generates said alarm signal for feeding to said
alarm assembly.
16. An electronic article surveillance ("EAS") system for detecting EAS
tags in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller and performing a function of causing
interrogation signals to be transmitted into the interrogation zone and a
function of causing signals to be received from the interrogation zone;
a central means communicating with said local means, said central means
including a central processing unit;
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated;
said local means performing in one of a plurality of diverse manners the
function of causing signals to be received from the interrogation zone;
and said central means responsive to one or more conditions performing a
function of instructing said local means to receive signals from the
interrogation zone in a particular one of said plurality of diverse
manners.
17. An EAS system in accordance with claim 16 wherein:
said one or more conditions include an electrical noise condition.
18. An EAS system in accordance with claim 16 wherein:
said local means includes: a plurality of receiving antennas; and switch
means having a plurality of states in which said switch means configures a
number of said plurality of receiving antennas to be connected in-phase
and/or out-of-phase;
and said central means responsive to said one or more conditions functions
to instruct said switch means to be in one of said plurality of states of
said switch means.
19. An EAS system in accordance with claim 18 wherein:
said central processing unit generates an antenna configuration instruction
corresponding to said one of said plurality of states of said switch
means;
and said microcontroller receives said antenna configuration instruction
and generates an antenna configuration signal which said microcontroller
transmits to said switch means to cause said switch means to take on said
one of said plurality of states.
20. An electronic article surveillance ("EAS") system for detecting EAS
tags in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller;
a central means communicating with said local means, said central means
including a central processing unit;
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated;
said local means performing the function of generating an alarm signal when
a determination is made that an EAS tag is in said interrogation zone; and
said central means performing the function of reporting to said local means
that a determination has been made that an EAS tag is in the interrogation
zone.
21. An electronic article surveillance ("EAS") system for detecting EAS
tags in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller and a selectively reconfigurable antenna
means;
a central means communicating with said local means, said central means
including a central processing unit and performing the function of
instructing said local means to select a particular one of the
configurations of the reconfigurable antenna means of said local means;
and
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated.
22. An EAS system in accordance with claim 21 wherein:
said reconfigurable antenna means is a receiver antenna means.
23. An EAS system in accordance with claim 21 wherein:
said central means performs the function of instructing said local means in
response to an electrical noise condition.
24. An EAS system in accordance with claim 21 wherein:
the reconfigurable antenna means of said local means includes a plurality
of receiver antennas configurable in a plurality of different
configurations in which a number of said plurality of receiver antennas
are connected in-phase and/or out-of-phase.
25. An EAS system in accordance with claim 24 wherein:
said central processing unit generates an antenna configuration instruction
corresponding to one of said plurality of different configurations;
and said microcontroller receives said antenna configuration instruction
and generates an antenna configuration signal which said microcontroller
transmits to said reconfigurable antenna means to cause said
reconfigurable antenna means to have said one of said plurality of
different configurations.
26. An electronic article surveillance ("EAS") system for detecting EAS
tags in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller;
a central means communicating with said local means, said central means
including a central processing unit;
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated;
an EAS tag deactivator means associated with said local means for
deactivating EAS tags;
and said microcontroller at said local means providing signals to and
receiving signals from said EAS tag deactivator.
27. An EAS system in accordance with claim 26 wherein:
said microcontroller provides signals to said EAS tag deactivator in
response to signals from said central processing unit;
and said microcontroller provides signals to said central processing unit
based on said signals received from said EAS tag deactivator.
28. An electronic article surveillance ("EAS") system for detecting EAS
tags in an interrogation zone, said EAS system comprising:
a local means associated with said interrogation zone, said local means
including a microcontroller;
a central means communicating with said local means, said central means
including a central processing unit;
said local means, using said microcontroller, and said central means, using
said central processing unit, sharing the performance of a plurality of
functions which together enable an EAS tag in said interrogation zone to
be detected and an alarm condition generated;
a user management interface associated with said local means;
and said microcontroller providing signals to and receiving signals from
said user management interface.
29. An EAS system in accordance with claim 28 wherein:
said microcontroller provides signals to said user management interface in
response to signals received from said central processing unit; and
said microcontroller provides signals to said central processing unit in
response to signals from said user management interface.
30. A local station for use in an EAS system for detecting EAS tags in an
interrogation zone, said EAS system including a central station
communicating with said local station and having a central processing
unit, said local station being associated with said interrogation zone and
comprising:
a communication port for receiving signals from and transmitting signals to
the central processing unit of said central station;
a microcontroller for communicating with said central processing unit
through said communication port and for performing one or more functions
associated with enabling an EAS tag in said interrogation zone to be
detected and an alarm condition generated;
first means for causing interrogation signals to be transmitted into said
interrogation zone and signals to be received from said interrogation
zone, said first means including processing means for processing signals
caused to be received by said first means;
said processing means including: at least one variable gain amplifier for
amplifying a received signal;
and said microcontroller providing signals to said variable gain amplifier
for setting the gain of said variable gain amplifier.
31. A local station for use in an EAS system for detecting EAS tags in an
interrogation zone, said EAS system including a central station
communicating with said local station and having a central processing
unit, said local station being associated with said interrogation zone and
comprising:
a communication port for receiving signals from and transmitting signals to
the central processing unit of said central station;
a microcontroller for communicating with said central processing unit
through said communication port and for performing one or more functions
associated with enabling an EAS tag in said interrogation zone to be
detected and an alarm condition generated;
first means for causing interrogation signals to be transmitted into said
interrogation zone and signals to be received from said interrogation
zone; said first means including processing means for processing signals
caused to be received by said first means;
said processing means including: a multiplexer for receiving a plurality of
received signals and selectively outputting a particular one of said
received signals for transmission to said central station;
and said microcontroller providing signals to said multiplexer for
instructing said multiplexer as to which one of said plurality of received
signals should be output by said multiplexer.
32. A local station for use in an EAS system for detecting EAS tags in an
interrogation zone, said EAS system including a central station
communicating with said local station and having a central processing
unit, said local station being associated with said interrogation zone and
comprising:
a communication port for receiving signals from and transmitting signals to
the central processing unit of said central station;
a microcontroller for communicating with said central processing unit
through said communication port and for performing one or more functions
associated with enabling an EAS tag in said interrogation zone to be
detected and an alarm condition generated;
first means for causing interrogation signals to be transmitted into said
interrogation zone and signals to be received from said interrogation
zone, said first means including a selectively reconfigurable antenna
means;
and said microcontroller in response to an antenna configuration
instruction from said central processing unit providing an antenna
configuration signal to said selectively reconfigurable antenna means to
cause said selectively reconfigurable antenna means to take on a
particular antenna configuration.
33. A local station in accordance with claim 32 wherein:
said selectively reconfigurable antenna means includes a plurality of
receiver antennas configurable in a plurality of different antenna
configurations in which a number of said plurality of receiver antennas
are connected in-phase and/or out-of-phase.
34. A local station in accordance with claim 32 wherein:
said selectively reconfigurable antenna means includes: a plurality of
receiver antennas; and switch means having a plurality of states in which
said switch means configures a number of said plurality of receiver
antennas to be connected in-phase and/or out-of-phase; and
said microcontroller in response to said antenna configuration instruction
from said central processing unit provides said antenna configuration
signal to said switch means to cause said switch means to be in the one of
said plurality of states corresponding to said particular antenna
configuration.
35. A local station for use in an EAS system for detecting EAS tags in an
interrogation zone, said EAS system including a central station
communicating with said local station and having a central processing
unit, said local station being associated with said interrogation zone and
comprising:
a communication port for receiving signals from and transmitting signals to
the central processing unit of said central station;
a microcontroller for communicating with said central processing unit
through said communication port and for performing one or more functions
associated with enabling an EAS tag in said interrogation zone to be
detected and an alarm condition generated; and
said microcontroller in response to a signal from said central processing
unit that an EAS tag is present in said interrogation zone generating an
alarm signal.
36. A local station in accordance with claim 35 wherein:
said local station further comprises an alarm assembly;
and said microcontroller couples said alarm signal to said alarm assembly.
37. A local station for use in an EAS system for detecting EAS tags in an
interrogation zone, said EAS system including a central station
communicating with said local station and having a central processing
unit, said local station being associated with said interrogation zone and
for further use with an EAS tag deactivator associated with that local
station for deactivating EAS tags, said local station comprising:
a communication port for receiving signals from and transmitting signals to
the central processing unit of said central station;
a microcontroller for communicating with said central processing unit
through said communication port and for performing one or more functions
associated with enabling an EAS tag in said interrogation zone to be
detected and an alarm condition generated; and
said microcontroller providing signals to and receiving signals from said
EAS tag deactivator.
38. A local station in accordance with claim 37 wherein:
said microcontroller provides signals to said EAS tag deactivator in
response to signals from said central processing unit;
and said microcontroller provides signals to said central processing unit
based on said signals received from said EAS tag deactivator.
39. A local station for use in an EAS system for detecting EAS tags in an
interrogation zone, said EAS system including a central station
communicating with said local station and having a central processing
unit, said local station being associated with said interrogation zone and
for further use with a user management interface associated with the local
station for controlling the EAS system and receiving information as to EAS
system status events, said local station comprising:
a communication port for receiving signals from and transmitting signals to
the central processing unit of said central station; and
a microcontroller for communicating with said central processing unit
through said communication port and for performing one or more functions
associated with enabling an EAS tag in said interrogation zone to be
detected and an alarm condition generated.
said microcontroller providing signals to and receiving signals from said
user management interface.
40. A local station in accordance with claim 39 wherein:
said microcontroller provides signals to said user management interface in
response to signals received from said central processing unit; and
said microcontroller provides signals to said central processing unit in
response to signals from said user management interface.
Description
BACKGROUND OF THE INVENTION
This invention relates to electronic article surveillance ("EAS") systems
and, in particular, to EAS systems which employ a central station for
system control.
In EAS systems of the above type, it is customary to provide the central
station with a central processing unit which has the responsibility for
performing all of the functions required to detect the presence of EAS
tags and to generate alarms based thereon. The EAS tag detection function
of the central processing unit is of critical importance and includes
complex signal and noise processing procedures. The alarm generation
function is less complex and may be characterized as a housekeeping
function. This function includes the generating of alarm signals and the
counting of alarms.
As EAS systems have become more sophisticated and the EAS tag detection
function has increased in complexity, increasing demands have been placed
on the central processing unit at the central station. This has prompted
designers to look for ways to lessen these demands without degrading EAS
system performance.
Also, in EAS systems of this type, when the receiver antennas are initially
installed they are manually configured, i.e., connected, so as to minimize
noise effects on the received signals. Thus, the receiver antennas are
connected either in-phase or out-of-phase so that their received signals
are either additive or subtractive. In locations where there is a great
deal of electrical noise, the out-of-phase connection is used, and in
locations where there is less electrical noise the in-phase connection is
used.
After initial installation, a change in the electrical noise conditions at
a location may warrant a change in the receiver antenna configuration,
i.e., from an in-phase connection to an out-of-phase connection or vice
versa. This is usually carried out by dispatching to the location a
maintenance person who can then manually change the receiver antenna
connections. However, since the electrical noise conditions in a location
can change from hour to hour and from day to day, the availability of a
maintenance person to manually change the receiver antenna configuration
to accommodate these changes becomes impractical.
In U.S. patent application Ser. No. 08/313,848 assigned to the same
assignee hereof, a technique is described for using a cross point switch
and inversion circuits to electrically simulate reconfiguration of the
receiver antennas of an EAS system. However, this requires additional
circuitry and processing at the central station again increasing the
demands on the central processing unit.
It is, therefore, an object of the present invention to provide an improved
EAS system.
It is a further object of the present invention to provide an EAS system in
which the demands placed on the central processing unit are made more
manageable.
It is yet a further object of the present invention to provide an EAS
system in which the receiver antennas can be readily reconfigured without
a significant additional burden being placed on the central processing
unit.
SUMMARY OF THE INVENTION
In accordance with the principles of the present invention, the above and
other objectives are realized in an EAS system by providing a local
station or means associated with the interrogation zone being monitored,
by providing a central station or means which communicates with the local
station, and by providing that the central station and the local station
share the performance of a plurality of functions which together enable an
EAS tag in the monitored interrogation location to be detected and an
alarm condition generated. More particularly, in accordance with the
invention, a central processing unit is included in the central station
and a microcontroller is included in the local station so that the sharing
of the plurality of the functions can be effected.
In one aspect of the invention, the central station using the central
processing unit performs the function of processing the signals received
at the local station and making a determination as to whether the received
signals contain signals generated by an EAS tag. The local station using
the microcontroller, in turn, performs the function of generating an alarm
signal, either audible, visual or both, upon an instruction from the
central processing unit that EAS tag signals are contained in the received
signals. The local station can also perform certain processing functions
on the received signals, e.g., amplification and selective transmission,
again in conjunction with the microcontroller and before the signals are
transmitted to the central station.
In a further aspect of the invention, the local station, via the
microcontroller, is adapted to effect configuration of the receiver
antennas associated with the local station, based on instructions from the
central processing unit at the central station. More particularly, the
central processing unit based on certain monitored conditions at the
location provides antenna configuration instructions to the
microcontroller at the local station. The microcontroller, in turn,
generates antenna configuration signals which control antenna
configuration switches which configure the receiver antennas so that a
number of receiver antennas are connected in-phase and/or out-of-phase,
depending upon the configuration signals.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features and aspects of the present invention will
become more apparent upon reading the following detailed description in
conjunction with the accompanying drawings, in which:
FIG. 1 shows an EAS system in accordance with the principles of the present
invention; and
FIG. 2 shows in greater detail the receiver antenna connections for certain
of the receiver antennas of FIG. 1.
DETAILED DESCRIPTION
FIG. 1 shows an EAS system 1 in accordance with the principles of the
present invention. The EAS system 1 is used to monitor an interrogation
zone 2. The interrogation zone 2 has associated with it four sets of
receiver antennas 3A-3B, 3C-3D, 3E-3F and 3G-3H and four sets of
associated transmitter antennas 4A-4B, 4C-4D, 4E-4F and 4G-4H.
The receiver antennas receive signals generated in the zone in response to
signals transmitted into the zone by the transmitter antennas. If an EAS
tag 5, such as, for example, a magneto-mechanical EAS tag of the type
described in U.S. Pat. No. 4,510,489, is located in the zone, the received
signals will contain EAS tag signals generated as a result of the
interaction of the EAS tag 5 with the transmitted signals.
A central station 6 including a central processing unit 7 performs a
plurality of control functions for the system 1. A primary function is a
signal processing function 7A by which it processes signals received by
the receiver antennas 3A-3H. Based on this processing, the central station
6 determines whether the received signals contain EAS tag signals and if
EAS tag signals are found, generates an alarm condition.
In accordance with the principles of the present invention, in order to
reduce the operating requirements on the central processing unit 7 which
become high as the signal processing function 7A becomes more complex, the
system I has been adapted to include a local station 8. More particularly,
the local station 8 includes a microcontroller or microprocessor 9 which
cooperates with the central processing unit 7 in the central station 6 in
controlling operation of the system 1.
Specifically, in further accord with the invention, the central station 6,
via the central processing unit 7, and the local station 8, via the
microcontroller 9, are adapted to share the functions required to
determine the presence of EAS tag signals and to generate alarm conditions
and alarms in the system 1. In the present embodiment, the local station 8
and microcontroller 9 take on a variety of functions one of which is
generating alarm signals, this function having previously been carried out
by the central station 6 and the central processing unit 7.
More particularly, once the processing function 7A of the central
processing unit 7 assesses the presence of EAS tag signals in the received
signals transmitted from the local station 8, the central processing unit
7 generates an alarm instruction signal or message. This signal or message
is transmitted by the central processing unit 7 to the microcontroller 9
at the local station 8 over a bidirectional serial communications path 11.
The microcontroller 9, in response to the alarm instruction signal, then
generates an appropriate alarm signal which it feeds to an alarm generator
12. The alarm generator 12, in turn, signals a local audio/visual alarm 13
which provides an alarm indication at the local station 8. As part of the
alarm signal generation function, the microcontroller 9 also determines
the specific timing for generating each alarm signal.
By using the local station 8 and the microcontroller 9 to perform the above
alarm function, the burden on the central processing unit 7 and the
central station 6 is reduced. Additionally, the other functions performed
by the local station 8 and microcontroller 9 to be discussed hereinbelow
also lessen the operating burden placed on the central processing unit 7.
More particularly, the local station and microcontroller are further
adapted to aid in providing signal processing and flow control of the
signals received by the receiver antennas 3A-3H, as well as antenna
configuration control of such antennas.
As shown in FIG. 1, the antenna pairs 3A-3B, 3C-3D, 3E-3F and 3G-3H are
connected to respective antenna configuration switches 14A-14D. These
switches feed the received signals from their respective antenna pairs to
respective variable gain amplifiers 15A-15D. The variable gain amplifiers
15A-15D are all connected to a multiplexer 16. The multiplexer 16
selectively couples the amplified received signals from the amplifiers to
an analog output line 17 which connects the local station 8 to the central
station 6.
The microcontroller 9 at the local station 8 is provided with control lines
9A, 9B and 9C for controlling the multiplexer 16, amplifiers 15A-15D and
antenna configuration switches 14A.14D. Specifically, based on instruction
signals generated by the central processing unit 7 at the central station
6 and conveyed to the local station 8 over the communications path 11, the
microcontroller 9 controls the multiplexer 16 so that it couples a
particular one of the amplifier outputs to the analog output line 17. In
this way, the received signals from the antenna pairs 3A-3B, 3C-3D, 3E-3F
and 3G-3H can be polled or scanned in sequence and delivered to the
central station 6.
Additionally, again based on signals from the central processing unit 7 at
the central station 6, the microcontroller 9 supplies suitable signals
over the line 9B for adjusting the gain of the respective amplifiers
15A-15D. The received signals from the antenna pairs can thus be suitably
signal processed by gain adjustment at the amplifiers 15A-15D at the local
station 8 before being sent to the central station 6 for further signal
processing. The central station and central processing unit 7 are thus
relieved from providing these functions.
The antenna configuration function of the local station 8 and
microcontroller 9 involves a further aspect of the invention in which the
local station is adapted to itself permit the establishing of the
configuration or connection of each pair of the receiver antennas 3A-3B,
3C-3D, 3E-3F and 3G-3H. This is accomplished via electronic configuration
switches 14A-14D which are fed antenna configuration signals over the line
9C from the microcontroller 9. These configuration signals are, in turn, a
result of antenna configuration instructions sent to the local station and
microcontroller 9 by the central station 6 and the central processing unit
7 over the communication path 11.
Each of the antenna configuration switches 14A-14D is adapted to have two
states. In a first state, the switch connects its respective pair of
receiver antennas so that they are in-phase and, hence, their received
signals are additive. In a second state, each switch connects its pair of
receiver antennas so that they are out-of-phase and, therefore, their
received signals are subtractive.
The particular configuration selected for each receiver antenna pair is
based on environmental conditions at the location being monitored by the
EAS system 1, including the electrical noise condition. These conditions
are reported to the central station 6 and based thereon the central
processing unit 7 generates antenna configuration instructions for the
respective antenna configuration switches.
Each antenna configuration instruction is fed over the communication path
11 to the local station 8 and the microcontroller 9. The microcontroller
9, in turn, relays a configuration signal over the path 9C to the
appropriate switch 14A to 14D. The switch thereupon takes on the
respective state as determined by the signal. This, in turn, results in a
change in the antenna connection, if the instruction signal indicates an
antenna connection which is different from the current connection.
In this way, the receiver antenna pairs 3A-3B, 3C-3D, 3E-3F and 3G-3H at
the local station 8 are automatically reconfigured. The necessity of
dispatching maintenance personnel for this purpose is, thus, eliminated
and the ability of the system to have receiver antenna connections best
suited for the current conditions is easily and readily realized.
It should be noted that the central processing unit 7 can monitor the
current conditions of the location and set the amplifier gains and the
antenna configurations in various ways. Suitable procedures for doing this
are disclosed in the aforementioned copending '848 patent application and
in U.S. patent application Ser. No. 08/313,849, (issued as U.S. Pat. No.
5,495,229 on Feb. 27, 1996) the teachings of both of which are
incorporated herein by reference.
FIG. 2 shows in greater detail the antenna configuration switches 14A and
14B and the manner in which they selectively interconnect the receiver
antennas pairs 3E-3F and 3A-3B. As can be appreciated, the switches 14A
and 14B include eight switch contacts 31-38 connected to differential
amplifiers 39 and 41. In the case shown, the contacts 31, 33, 36 and 38
are closed and the contacts 32, 34, 35 and 37 are opened. With the
contacts in these states, the antennas 3E and 3F are serially connected
in-phase, while the antennas 3A and 3B are serially connected
out-of-phase.
By opening the contacts 31, 33, 36 and 38 and closing the contacts 32, 34,
35 and 37, the antenna configurations are changed. In these states of the
contacts, the antennas 3E and 3F are serially connected out-of-phase and
the antennas 3A and 3B are connected in-phase.
The antenna configuration signals from the microcontroller 9 and carried
over the line 9C provide the signals A-D for controlling the contacts
31-38. Appropriate selection of the signals results in the desired contact
closures and the desired antenna configurations.
As can be appreciated, in the present embodiment, each of the switches
14A-14D only permits in and out-of-phase connection of a pair of antennas.
However, it is within the contemplation of the invention to provide
configuration switches in which each antenna can be connected in and
out-of-phase with more than one of the other antennas.
In the embodiment of the invention shown in FIG. 1, the microcontroller 9
at the local station 8 also functions to couple messages between the
central processing unit 7 at the central station 6 and a management
interface 18 and an EAS tag deactivator 19. This occurs through buffer
drivers 21 and 22, respectively.
In this way, the microcontroller 9 can provide enable and disable signals
to the EAS tag deactivator 19 based on enable and disable instructions
from the central processing unit 7. The microcontroller 9 can also provide
to the central processing unit 7 information as to EAS tag deactivations
based on tag deactivations reported to the microcontroller by the
deactivator.
The microcontroller 9 additionally can relay information as to system
status events received from the central processing unit 7 to the user
management interface 18 based on requests for information from the
interface. Finally, signals for controlling operation of the EAS system
generated at the interface 18 can be relayed by the microcontroller 9 to
the central processing unit 7 for action by the unit.
In the present illustrative case, communication between the central
processing unit 7 and the microcontroller 9 is by way of bi-directional
serial communications paths 11. This path can also be a parallel
communication path, if desired.
The microcontroller 9 can typically be a Motorola 68HC811E2 provided with
the appropriate software programming to accommodate the desired shared
functions to be performed by the microcontroller. The central processing
unit 7 can typically be an Intel 80386/486-40 with appropriate software
programming to perform its signal processing function and other functions
to effect EAS signal determinations.
In all cases it is understood that the above-described arrangements are
merely illustrative of the many possible specific embodiments which
represent applications of the present invention. Numerous and varied other
arrangements, can be readily devised in accordance with the principles of
the present invention without departing from the spirit and scope of the
invention. Thus, for example, the local station 8 via the microcontroller
9, can be further adapted to provide additional signal processing of the
received signals such as, for example, signal conditioning, signal
enhancement and preliminary signal decisions. It also could be adapted via
the microcontroller to provide a part of the EAS tag signal determination
function (including processing a part of the EAS tag signal determination
algorithm) for the received signals.
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